1. Field of the Invention
The present invention relates to wheel hubs such as those used in the front wheels of four wheel drive automotive vehicles, in which the wheel can be either locked to its related drive axle, or arranged so as to be able to overrun its drive axle.
2. Description of the Prior Art
In four wheel drive automotive vehicles, it is sometimes desirable to have all four wheels fixedly connected to their drive axles, for example, in a situation where the vehicle is traveling over quite difficult terrain, or when compression braking is needed. However, in many situations where the vehicle is traveling over a paved road surface, it is more advantageous to disengage the front wheels, so that they can rotate independently of their drive axle or at least overrun the axle. Accordingly, there appears in the prior art a number of wheel locking hubs which permit the front wheels of a four wheel drive vehicle to operate in both locked and unlocked modes.
For example, in U.S. Pat. No. 2,684,140 there is shown a wheel hub that has an overrunning interior clutching member through which the drive axle can transmit power to the front wheel, but which permits the front wheel to freely overrun the drive axle. Additionally, there is a locking mechanism which can selectively be moved into locking engagement to form a positive mechanical connection between the driving and driven portions of the hub so as to rigidly lock the wheel to the drive axle. U.S. Pat. No. 2,884,101 shows a substantially similar system with the addition of an O-ring to cause frictional engagement between the roller cage of the clutch mechanism with stationary structure. U.S. Pat. No. 3,055,471 shows yet another hub similar to the two mentioned above, but with a set of friction shoes to cause frictional engagement of the roller cage of the clutching mechanism with stationary structure.
U.S. Pat. No. 3,351,364 illustrates a hub lock having a first position where the outer housing that is connected to the wheel can rotate completely independently of its associated drive axle. There is a locking member movable toward the hub member to move a set of dowels into grooves formed between the driving hub and the outer housing to cause a positive locking engagement. Three other hub locks similar to that shown in U.S. Pat. No. 3,351,364 are shown in the following three patents: U.S. Pat. No. 3,442,361, U.S. Pat. No. 3,753,479 and U.S. Pat. No. 3,718,213. In these three last named patents, there is a locking mechanism which is moved axially into and out of locking engagement through a spring connection with its actuating member. Thus, if at the time the actuating member is moved to its lock position, there is misalignment between the components, the actuating spring remains stressed until the components shift into alignment, at which time the locking mechanism goes into engagement.
In U.S. Pat. No. 3,123,169 there is shown a wheel hub having an overrunning clutch mechanism comprising an interior driving hub connected to a drive axle, an outer housing connected to the driven wheel, and a roller clutch assembly mounted therebetween. There is friction means engaging the roller cage to cause clutching engagement between the driving hub and the housing when the axle is rotated under power. In its free wheeling mode, the wheel is permitted to overrun its related axle, with the roller clutch assembly moving out of clutching engagement. Thus hub also has a lock position which is accomplished by a magnetically actuated plate causing a friction ring to engage the cage of the roller clutch assembly and thus cause engagement between the housing and the cage of the clutch assembly. With this friction plate causing the cage to rotate with the housing, the clutch assembly effectively locks the housing to the drive hub.
There is also shown in U.S. Pat. No. 3,123,169 a somewhat similar arrangement which, instead of providing frictional interconnection between the roller cage of the clutch assembly and the driven housing, provides a positive mechanical interlock between such members. This is accomplished by providing a locking finger in the driven housing which protrudes inwardly to engage the roller cage.